1. Field of the Invention
The present invention relates to optical communication by routing optical packets using multiple wavelength labels. More particularly, the present invention relates to a method for routing optical packets using multiple wavelength labels that is based on wavelength division multiplexing (WDM), to an optical packet router using multiple wavelength labels, and to an optical packet network that uses multiple wavelength labels.
2. Description of the Prior Art
In the area of optical packet communications using optical fibers, photonic networks have been proposed in which not only trunk line links, but even switching functions in network nodes connecting a plurality of trunk lines, are implemented in the optical domain. In such a network, when each of the optical packets passes through a network node, it can autonomously switch to a predetermined route based on address information carried by the packet. In this respect, there is a need for an optical packet routing system that optically labels each packet with the respective address, checks and identifies the labels in the optical domain and, based on the identification result, switches the output route of the packet.
In prior art photonic networks based on the WDM technology, many configurations and methods have been proposed in which the routing labels are comprised as single wavelength optical signals. To identify the packet labels, this technology uses simple wavelength identification devices such as arrayed waveguide gratings (AWG), which are limited with respect to the number of labels that can be identified. Specifically, when single wavelength labels are used, with the existing level of technology, most networks can only handle around 100 to 200 labels, and the upper limit for any network is around 1000.
For the processing involved, there has been proposed a label switching router employing a phase code processor that uses an optical code division multiplexing (OCDM) system (K. Kitayama and N. Wada, “Photonic IP Routing,” IEEE Photon. Technol. Lett., vol. 11, no. 12, pp. 1689–1691, December 1999). In that system, the labels used are phase labels having a pattern comprised of a light phase, such as 0, π, for example, so that the labels are, for example, “000π”, “00ππ”, “0π0π,” and so forth, which are processed by a phase code processor. An input signal constituting a phase label is split into a plurality of signals, each of which falls incident on an independent optical correlation processor. Each of these optical correlation processors is configured to match, i.e. identify, a corresponding independent phase label. This differs from the present invention in terms of label configuration method and label processor.
With respect to optical encoding using time spreading/wavelength hopping codes, Japanese Patent No. 3038378 discloses a method in which streams of optical pulses having different wavelengths on a bit-by-bit basis are used for encoding by setting different codes within a code sequence specified for each channel, with decoding of received signals being effected by matched filtering in the time domain. This disclosure differs from the present invention in that the disclosure does not pertain to routing.
As described above, with respect to prior art optical packet routing methods and apparatuses, and optical packet network configurations, with current technology, when single wavelength labels are used, most networks can only handle around 100 to 200 labels, and the upper limit for any network is around 1000 labels.